Gutted Cats
Street Queen to the extr3m3
Joined: Jan 2005
Posts: 4,554
Likes: 3
From: Lubbock, Texas
I disagree with ken, i did this to my truck and i noticed a diffrence in truck power and responsiveness. My cat was might plugged up though.
I cut my cat out with a sawzall.
Took a piece of big rebar and stuck it into the cat, hammered it down, pulled out moved repeated about 5-6 times, then started ramming rebar, down into cat and loosing comb. Picked up cat and hit the side of it with a rubber mallet and comb would come out the bottom repeated this cycle for about 45min to an hour before i was done.
I did notice power and tone diffrence in my truck but my cat was real plugged from mud and water and such. (long story)
I cut my cat out with a sawzall.
Took a piece of big rebar and stuck it into the cat, hammered it down, pulled out moved repeated about 5-6 times, then started ramming rebar, down into cat and loosing comb. Picked up cat and hit the side of it with a rubber mallet and comb would come out the bottom repeated this cycle for about 45min to an hour before i was done.
I did notice power and tone diffrence in my truck but my cat was real plugged from mud and water and such. (long story)
Freshman User
Joined: Oct 2007
Posts: 47
Likes: 0
The only other way would be to cut a 3 sided square (2 1/2" X 2 1/2") towards the back bottom of the converter. Lift the flap up and knock everything out of it with a long punch or chisel, if there's a screen in there, get that out too. Then knock the flap back down, turn your welder down low and weld the flap closed. It's very hard to weld so you should be a pretty good welder if you want to attempt this method. It's a hard, dusty, nasty job and the truck will have a hollow sound. If your cat is not clogged, you'd be doing a lot of work with little if any benefit.
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Posting Guru
Joined: Jun 2002
Posts: 1,214
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From: Rio Rancho USA
But that doesnt fix the problem of the open chamber that the exhaust now has to go through, expand, cool, and then try to get back through to go through the rest of the system.
A gutted cat is bad for flow. Again, there is no logical reason to do it when there are inexpensive high flow cats, or just leave the damn thing alone. They flow better than most poeple realise.
I could think of plenty of other areas that the effort / gains ratio would be much better.
A gutted cat is bad for flow. Again, there is no logical reason to do it when there are inexpensive high flow cats, or just leave the damn thing alone. They flow better than most poeple realise.
I could think of plenty of other areas that the effort / gains ratio would be much better.
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Street Queen to the extr3m3
Joined: Jan 2005
Posts: 4,554
Likes: 3
From: Lubbock, Texas
i would like to here some of these kens, I do know that a newer factory cat will flow good. But older cats do plug up over time. Where else do you get bettflow in a factory system.
Posting Guru
Joined: Jun 2002
Posts: 1,214
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From: Rio Rancho USA
Headers. Much better reward for the effort.
Most Y pipes suck. A better flowing one will sometimes give better gains than headers.
Whats the point of gutting a cat if you still have the restrictive muffler and pipe? Upgrade those and get better gains.
If your talking cheap mods, I would rather spend my time opening up the intake side, getting rid of resonators and restrictions that are on some intake tubing, add some timing, or just tune the engine up. Even someone with little mechanical knowledge can cut a stock muffler off and clamp a better flowing one in its place. All can give better gains than a gutted cat.
My .02 is that it is only half the job. At the very least weld a pipe inside the cat so flow isnt disturbed. In your case if it was that plugged up I can understand why you gutted it. I just dont understand the people on here that constantly want to remove or gut a perfectly good piece when it really isnt needed.
Most Y pipes suck. A better flowing one will sometimes give better gains than headers.
Whats the point of gutting a cat if you still have the restrictive muffler and pipe? Upgrade those and get better gains.
If your talking cheap mods, I would rather spend my time opening up the intake side, getting rid of resonators and restrictions that are on some intake tubing, add some timing, or just tune the engine up. Even someone with little mechanical knowledge can cut a stock muffler off and clamp a better flowing one in its place. All can give better gains than a gutted cat.
My .02 is that it is only half the job. At the very least weld a pipe inside the cat so flow isnt disturbed. In your case if it was that plugged up I can understand why you gutted it. I just dont understand the people on here that constantly want to remove or gut a perfectly good piece when it really isnt needed.
Former ******
Joined: Nov 2004
Posts: 4,901
Likes: 2
From: Salt Lake City, Utah
If your old cat is in good condition, ther eis no reason to replace or gut it. Doing so is illegal. If you are looking for maximum performance, you really need to approach the exahust system as a whole. It will only flow as well as its weakest point, and in factory systems, those weak points are the factory y-pipes and the factory muffler.
A gutted cat will only perform better if it was previously plugged. Don't confuse an increase in sound levels with performance. If it was my vehicle, I would replace it with a high flow cat, and even then, only if something was wrong with the original or I was doing some other modification that would require the cat replacement.
A gutted cat will only perform better if it was previously plugged. Don't confuse an increase in sound levels with performance. If it was my vehicle, I would replace it with a high flow cat, and even then, only if something was wrong with the original or I was doing some other modification that would require the cat replacement.
Street Queen to the extr3m3
Joined: Jan 2005
Posts: 4,554
Likes: 3
From: Lubbock, Texas
Good info kens, I do agree to aproaching an exhaust system as a whole. Do you think you get better power with mufflers and cats as apposed to a straight piped exhasust system? Not talkin legalities here, just performance gains or losses. From a high flow cat and a good quality muffler and the same exhaust system just with straight pipes. Performance loss, or performance gains? I do also agree with the opening up of the intake side also, i know my stock intake was very restrictive it had a 1"x4" slot for the intake, bye bye stock, hello K&N. Suggestions on timing advancement?
Former ******
Joined: Nov 2004
Posts: 4,901
Likes: 2
From: Salt Lake City, Utah
Originally Posted by Truckin4life
Good info kens, I do agree to aproaching an exhaust system as a whole. Do you think you get better power with mufflers and cats as apposed to a straight piped exhasust system? Not talkin legalities here, just performance gains or losses. From a high flow cat and a good quality muffler and the same exhaust system just with straight pipes. Performance loss, or performance gains? I do also agree with the opening up of the intake side also, i know my stock intake was very restrictive it had a 1"x4" slot for the intake, bye bye stock, hello K&N. Suggestions on timing advancement?
There are a few converter systems out there that are restrictive. Any GM with a bead type converter is highly restrictive. That is why Ford doesn't use them. Also the large converters, that we in the industry refer to as a torpedo, found on Ford trucks with either the 5.8L heavy duty models, and all 7.5L under 10,000 lbs, plus many of the 6.8L and the heavy duty 5.4L are highly restrictive by virtue of their size. These converters have such a large cross section that they act as an expansion chamber, plus there are three bricks inside what offer resistance to the air passing through. Since the gases have to slow down so much because of the cross section, the friction of the catalyst can be significant. In cases such as bead types and torpedos, there are high flow converters that are smaller and less restrictive.
